The present invention relates to an integrated control safety valve, placed on an enclosure containing a pressurized fluid. It makes it possible to limit the pressure inside the enclosure. In the case of an overpressure, the valve opens, which makes it possible to discharge a fluid quantity from the enclosure and consequently limit the pressure within the same.
Safety valves, which are also called pressure relief valves, comprise a clapper, clack or flap constituted e.g. by a ball, which seals an orifice and which is kept on its seat by a bearing plunger or piston moved by a spring. The force exerted by the spring can be regulated by means of a screw, which compresses it to a greater or lesser extent. It is in this way possible to regulate the pressure from which the ball rises from its seat. Such a valve is mounted on the wall of an enclosure containing a pressurized fluid. When the pressure within this enclosure exceeds a predetermined value, the ball lifts and the fluid contained in the enclosure flows out of the same. This prevents any risk of damage, which could occur in the case of an overpressure within the enclosure.
A disadvantage of such valves is that they instantaneously react to the pressure variations prevailing within the enclosure. Thus, the flaps are released on a number of occasions, even for the purpose of discharging a very small fluid quantity. The resulting jarring can lead to a deterioration of the seat.
This problem is obviated by integrated control safety valves, which comprise a main flap, by which the fluid is evacuated from the enclosure and a control device. The opening of the main flap is controlled by the control device, which is set to the pressure value prevailing within the enclosure.
As a result of this arrangement, the control valves operate on a hit or miss basis, i.e. the main flap is either open or closed and there is no intermediate position. Thus, risks of jarring are limited and the life of the valve is increased.
The invention relates to an integrated control safety valve for an enclosure containing a pressurized fluid, the valve incorporating a valve body fixed to a wall of the enclosure, the body being provided with an inlet and an outlet for the fluid, the inlet communicating with the pressurized enclosure, whilst the outlet is to the atmosphere, said body defining a chamber linking the inlet and the outlet, a valve placed in the chamber interrupting the connection between the inlet and the outlet, whereby the valve comprises a stem, a main flap integral with the stem and able to seal a seat positioned between the inlet and the outlet and a plunger integral with this stem and sliding in the chamber, elastic means for applying the main flap to the seat, a channel passing axially through the valve, a control flap sealing the channel traversing the valve, elastic means for applying the control flap to the orifice and an orifice connecting the chamber to the atmosphere.
An integrated control valve of this type is known (GB-A No. 700,198). This valve comprises a body 5, an inlet which can be connected to a hydraulic circuit and an outlet 7 for the fluid. The upper chamber 8 and the lower chamber 9 are separated by an autoclave-type valve 12. Valve 12 has an axial passage 15 closed by a second valve 17 having a smaller passage cross-section. When this valve opens, it enables the fluid to penetrate a chamber closed by a plunger 27, which controls the opening of the valve. An orifice 65 connects the annular space 50, i.e. the chamber, with the lower chamber 9, which is connected to the discharge pipe 7. Orifice 65 has a small diameter, so as to prevent a rapid pressure drop during the control of the valve.
However, in this valve, orifice 65 remains permanently open. When there is an overpressure in the pressurized container, flap A opens and the fluid enters chamber 50. However, in view of the fact that orifice 65 remains permanently open, the fluid is simultaneously discharged by this orifice. Thus, there is a delay in the pressure rise in chamber 50, so that the opening of the main flap is also delayed. Thus, there is a time lag between the appearance of the overpressure in the enclosure and the opening of the main flap. Conversely, at the end of the overpressure, the pressure in chamber 50 drops rapidly. Thus, the auxiliary valve 17 is suddenly closed, so that there is a risk of damage to its seat.